What was the name of the theory that said that if one country in a region fell to Communism, others would surely follow?

domino theory

The domino theory was a theory prominent from the 1950s to the 1980s that posited that if one country in a region came under the influence of communism, then the surrounding countries would follow in a domino effect.

Explanation:

in 1803 the louisiana purchase took place, doubling the size of the country. by 1840 almost 7 million americans had migrated westward in hopes of securing land and being prosperous. the belief that settlers were destined to expand to the west is often referred to as manifest destiny.

explanation:

yes they have. but is this a true false question? if it is, the answer is true.